1. Field of the Invention
This invention relates to a motorcycle having a fuel tank formed with a filler opening facing upward.
2. Description of Related Art
Conventionally, a fuel tank on a motorcycle has a filler opening at its upper end facing upward. Fuel is poured into the tank through the filler opening by inserting a filling tube of the fueling gun or of the portable fuel tank into the filler opening. While pouring, a refueling person checks the fuel level within the fuel tank through a gap between the filler opening and the filling tube to determine if the desired fuel level has been reached or not.
In recent years, some motorcycles have been provided with an air cleaner below the fuel tank. The fuel tank in this type of motorcycle has a relatively shallow depth in the area above the air cleaner. The filler opening is often formed in this area of shallow depth, and sometimes in the course of refueling, part of the fuel bounces back after hitting the bottom face of the tank and turns into fine particles that are spattered out of the fuel tank through the filler opening.
Fuel that is spattered out of the fuel tank adheres to and contaminates the outer surface of the fuel tank. Therefore, in fuel tanks having a shallow depth below the filler opening, fuel bouncing back in the course of refueling adheres to the external surface of the fuel tank and creates a problem in that the adhered fuel must be wiped off each time.
JP-B-3214654 discloses a fuel tank configuration to prevent fuel from bouncing back. In JP-B-3214654, a guide groove is formed on the bottom wall of the fuel tank opposite to the filling opening, for leading the fuel slantingly downward to the rear. The guide groove is formed in such shape that part of the bottom wall of the tank is downwardly swelling out, and is constituted with a concave groove having a cross section of circular arc. The inner surface of the guide groove is formed into a concave curve.
However, even when such a guide groove is formed on the bottom wall of the fuel tank, fuel hitting the wall of the guide groove constituted with a concave curve may still bounce back upward and spatter out of the filling opening. The amount of fuel spattering out of the tank may be reduced by forming the filler opening with a smaller bore. Such design, however, hinders the visual check of the fuel level in the course of refueling.
In addition, the fuel tank of JP-B-3214654 leads to the problem of reduced air cleaner capacity, because the upper wall of the air cleaner, located below the fuel tank, is concaved to avoid interference with the bottom wall of the fuel tank opposite to the filler opening, which is projected downward by the depth of the guide groove.